1. Field of the Invention
The present invention relates to an installation enabling the passage through a water ramp by boats navigating a canal to be accelerated, this acceleration being obtainable at the level of the upstream end and/or of the downstream end of the water ramp.
The invention relates also to a method particularly applicable to the abovesaid installation.
2. Description of the Prior Art
It is known that a water ramp is an engineering construction designed to replace locks when an inland waterway must pass through a considerable change in level.
The water ramp includes, between the downstream stretch or reach and the upstream reach--which is necessarily closed downstream by a gate--an inclined channel (also called a "trench"), with a substantially rectangular cross-section, whose walls (called "lock-walls") and bottom (also called "bed") are of masonry.
Along this channel, a pusher runs over runways driving a panel called a "mask" (or "shield") transversely obturating the channel. The mask constitutes a substantially fluid-tight closure of the channel, so that it can retain on its upstream surface a certain volume of water. By reason of the slope, the longitudinal vertical cross-section of this volume is triangular and the water mass is in the form of a wedge. A boat floating on this water-wedge, which thus constitutes a movable reach, is lifted or lowered therewith when the pusher is moved along the channel. By its to-and-fro movement, the movable reach ensures the transfer of boats from the downstream stretch to the upstream stretch and vice-versa.
It is particularly for the passage through a considerable change in level that the construction of a water ramp becomes more advantageous than that of a simple lock or a storage basin lock.
Consideration of the duration of the cycle is important, both as regards the lock and as regards the water ramp. It is known that this duration is that which runs between transits of a certain point by two boats or by two convoys navigating in the same direction.
In the case of a lock, the duration of the cycle is equal to the sum of the elementary times corresponding to the following operations, which must necessarily succeed one another:
at the downstream head, the exit of the descending boat and the entrance of the ascending boat, PA1 closing of the downstream gate, PA1 filling of the lock, PA1 opening of the upstream gate, PA1 at the upstream end, exit of the ascending boat and entrance of the descending boat, PA1 closing of the upstream gate, PA1 emptying of the lock, PA1 opening of the downstream gate. PA1 four gate operations, PA1 filling and emptying of the lock, PA1 exchanges of boats upstream and downstream.
In summary, the duration of the cycle of a lock comprises:
In the cycle of a water ramp, similar elements are again found.
The gate operations, which are rapid in the case of a lock, are still faster in the case of a water ramp. Their duration is not even to be reckoned separately, since they are carried out at the same time as the water flows.
The filling and emptying of the lock are replaced by the ascent and descent of the water-wedge. At the present time, the movement of this wedge at a higher speed than three meters per second is not contemplated. Especially for very high water ramps, these movements require more time than the filling and emptying of the lock, of which operations the speed is however limited by the necessity of not removing or of injecting, into the stretches situated upstream and downstream of the structure, flow rates higher than those which produce in said stretches currents acceptable by boats in movement or stationary.
The boat exchanges at the two heads correspond, in the case of locks, to a very large fraction of the duration of the cycle. As will be seen, these exchanges can be faster in the case of water ramps and it is a specific object of the present invention to accelerate these exchanges.
To reduce the duration of the cycle of water ramps, it is advantageous to exploit to the maximum this possibility of reducing the time of the exchanges. It will be noted particularly that, in the matter of locks, the movements of boats are necessarily rather slow, because they are carried out by using exclusively the own engines of these boats, whose power is small relative to the masses to be moved. In the matter of water ramps, it is indicated to use in addition, for these movements, the considerable power of the pusher.
The expulsion of the boat or of the convoy, which must emerge from the water-wedge, is relatively easy, whilst the operation of introduction is complicated by the fact that the waiting boat stands in a lateral position with respect to the axis of navigation, which coincides with the axis of the inclined channel. Now, this axis of navigation must, in the first stage, be reserved for the emerging boat. After its exit, a lateral movement of the waiting boat is necessary before the latter can be introduced into the water-wedge.
This necessity has been taken into account in French Pat. No. 73 33932 of Sept. 21, 1973 of Applicant.
This patent relates to arrangements of the water ramp and the method relating thereto applicable both to the upstream end and the downstream end of the water ramp. These arrangements will be recalled below to distinguish them well from the present invention, considering only, for simplification, the upstream end.
At the downstream end of the upstream stretch, immediately upstream of the tilting gate, there is provided on the right bank a boat storage basin. The latter is constituted by a wall of the bank of which the waiting boat hauls alongside. This wall is pierced with orifices, so that the water can pass from the channel into a tank situated on the other side of the wall, or conversely. The tank is extended by a branch ending just downstream of the tilting gate, a gate enabling communication to be established or suppressed.
A second tank is arranged on the left bank, opposite the first, or a little more downstream. It is limited by a wall pierced with orifices and it is also extended by a branch closed by a gate at its end. By opening said gate, water is removed to the outside of the structure.
These two tanks are utilized to create a rectilinear transverse water current moving the boat which is stationary in the basin, from the right hand bank towards the left hand bank, so that it may become positioned substantially on the axis of the trench. To do this, water is sent into the right bank pipe and the gate which closes that of the left hand bank is opened.
The water supply of the pipe of the right hand bank is obtained by causing the mask to advance upstream in the direction of the tilting gate, which has been lifted and locked in vertical position immediately after the exit of the ascending boat. This movement of the mask reduces the volume comprised between it and the tilting gate, so that the water escapes laterally into the branch.
When the positioning of the descending boat substantially on the axis of the trench has been accomplished, it remains to cause it to enter the latter. This second movement is obtained by closing the gates of the two branches, by opening the tilting gate and by moving the mask from upstream to downstream. In this way an aspiration is created which draws the boat, the latter using its engine simultaneously.
The experiment carried out at the Montech site, in France, showed Applicant that this method was effective, but that it was not fully satisfactory, if only by reason of the civil engineering costs involved in the construction of two tanks. On the other hand, it is difficult in the transverse movement of the boat which should be a simple translation, to avoid a certain rotation. The creation of the transverse current results also in a troublesome loss of water. Finally, the fact that the boat no longer has appreciable speed at the beginning of the withdrawal does not permit it to become engaged fast enough in the intermediate space situated downstream of the tilting gate.
It is an object of the present invention to overcome these drawbacks by a simple and relatively uncomplicated installation and by means of an easy method of operation, fully profiting from the capacity of the pusher driving the mask.
It is also an object of the invention to exploit the means thus provided to limit as much as possible the volume of the water-wedge transported, for given boat length and draft, whilst avoiding certain difficulties connected with the passage of the water-wedge from the top of the inclined channel to the horizontal upstream stretch.